A Finite Element Model for Direction-Dependent Mechanical Response to Nanoindentation of Cortical Bone Allowing for Anisotropic Post-Yield Behavior of the Tissue

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
D. Carnelli ◽  
D. Gastaldi ◽  
V. Sassi ◽  
R. Contro ◽  
C. Ortiz ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Cortical Bone ◽  
Yield Stress ◽  
Bone Tissue ◽  
Mechanical Response ◽  
Experimental Studies ◽  
Element Model ◽  
Yield Behavior ◽  
Constitutive Parameters

A finite element model was developed for numerical simulations of nanoindentation tests on cortical bone. The model allows for anisotropic elastic and post-yield behavior of the tissue. The material model for the post-yield behavior was obtained through a suitable linear transformation of the stress tensor components to define the properties of the real anisotropic material in terms of a fictitious isotropic solid. A tension-compression yield stress mismatch and a direction-dependent yield stress are allowed for. The constitutive parameters are determined on the basis of literature experimental data. Indentation experiments along the axial (the longitudinal direction of long bones) and transverse directions have been simulated with the purpose to calculate the indentation moduli and the tissue hardness in both the indentation directions. The results have shown that the transverse to axial mismatch of indentation moduli was correctly simulated regardless of the constitutive parameters used to describe the post-yield behavior. The axial to transverse hardness mismatch observed in experimental studies (see, for example, Rho et al. [1999, “Elastic Properties of Microstructural Components of Human Bone Tissue as Measured by Nanoindentation,” J. Biomed. Mater. Res., 45, pp. 48–54] for results on human tibial cortical bone) can be correctly simulated through an anisotropic yield constitutive model. Furthermore, previous experimental results have shown that cortical bone tissue subject to nanoindentation does not exhibit piling-up. The numerical model presented in this paper shows that the probe tip-tissue friction and the post-yield deformation modes play a relevant role in this respect; in particular, a small dilatation angle, ruling the volumetric inelastic strain, is required to approach the experimental findings.

scholarly journals Identification of Viscoelastic Constitutive Parameters of a Cell Based on Fluid-Structure Coupled Finite Element Model and Experiment

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Jun Qiu ◽  
Fang-Fang Li
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Single Cell ◽  
Mechanical Response ◽  
Element Model ◽  
Response Curves ◽  
Fluid Structure ◽  
Viscoelastic Parameters ◽  
A Cell ◽  
Constitutive Parameters

Although mechanical properties of a single cell as well as its mechanical response to stimulation are significant for mechanotransduction, it is difficult to quantitatively identify the viscoelasticity of a cell. This study proposes a methodology to determine the viscoelastic parameters for a single cell combining flow chamber experiment and fluid-structure coupled finite element model. The observation from the experiment is used to compare with the deformation response of the cell with different parameters in the finite element model with standard linear solid constitute model, which are adjusted until the two displacement response curves from the experiment and the simulation accord with each other, and then the corresponding combination of the viscoelastic parameters is determined to represent the viscoelasticity of the cell. The proposed methodology is applied on osteocytes in this study but can be generalized to other cells. The results indicate that both k1 and k2 of an osteocyte are in the order of several hundred Pa and η is in the order of kPa·s.

scholarly journals Biaxial estimation of biomechanical constitutive parameters of passive porcine sclera soft tissue

2021 ◽  
Author(s):  
Zwelihle Ndlovu ◽  
Dawood Desai ◽  
Thanyani Pandelani ◽  
Harry Ngwangwa ◽  
Fulufhelo Nemavhola
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Finite Element Model ◽  
Test Data ◽  
Element Model ◽  
Finite Element Models ◽  
Anisotropic Model ◽  
Material Models ◽  
Material Parameters ◽  
Constitutive Parameters

This study assesses the modelling capabilities of four constitutive hyperplastic material models to fit the experimental data of the porcine sclera soft tissue. It further estimates the material parameters and discusses their applicability to a finite element model by examining the statistical dispersion measured through the standard deviation. Fifteen sclera tissues were harvested from porcine’ slaughtered at an abattoir and were subjected to equi-biaxial testing. The results show that all the four material models yielded very good correlations at correlations above 96 %. The polynomial (anisotropic) model gave the best correlation of 98 %. However, the estimated material parameters varied widely from one test to another such that there would be needed to normalise the test data to avoid long optimisation processes after applying the average material parameters to finite element models. However, for application of the estimated material parameters to finite element models, there would be needed to consider normalising the test data to reduce the search region for the optimisation algorithms. Although the polynomial (anisotropic) model yielded the best correlation, it was found that the Choi-Vito had the least variation in the estimated material parameters thereby making it an easier option for application of its material parameters to a finite element model and also requiring minimum effort in the optimisation procedure. For the porcine sclera tissue, it was found that the anisotropy more influenced by the fiber-related properties than the background material matrix related properties.

scholarly journals Investigation of Beam Column Joint with Beam Weak in Shear under Monotonic Loading

2018 ◽  
Vol 7 (2.20) ◽  
pp. 182
Author(s):  
B Mounika ◽  
P Poluraju
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Main Parameter ◽  
Analytical Study ◽  
Experimental Studies ◽  
Element Model ◽  
The Other ◽  
Shear Reinforcement ◽  
Weak Beam ◽  
Column Joint

Earthquake affected structures, mostly failure occur at beam column joints (BCJ). BCJs are categorized according to their geometrical grouping as Interior, Exterior, and Corner joints. Exterior beam column joint (i.e., terminating the beam on one of the column faces) was the most vulnerable one with respect to the plane of loading. The present study aims at ductility behaviour of exterior BCJ with conventional reinforcement using the code IS 456-2000 and with special confining reinforcement using the Code IS 13920-2016. Four number of beam-column joint specimens are considered in which the first one is detailed as per IS 456-2000, the second one as per IS 13920-2016 and the other two with 50% and 30% reduction of shear reinforcement was provided while compared with the first specimen. It is mainly to satisfy the strong column-weak beam concept as the main parameter. The test was carried out on the loading frame with hinged conditions to the column both ends, and the load is applied at the tip of the beam. The experimental studies are proven with an analytical study carried out by finite element model by using ANSYS and disparate parameters are assessed both experimentally and analytically.  

scholarly journals A Novel Method for Tooth Bending Stress Calculation of Gears With Asymmetric Teeth

2021 ◽  
Author(s):  
Oguz DOGAN ◽  
Celalettin YUCE ◽  
Fatih KARPAT
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Experimental Studies ◽  
Element Model ◽  
Bending Stress ◽  
Element Analysis ◽  
Stress Calculation ◽  
Bending Stresses ◽  
New Equation ◽  
Asymmetric Factor

Abstract Today, gear designs with asymmetric tooth profiles offer essential solutions in reducing tooth root stresses of gears. Although numerical, analytical, and experimental studies are carried out to calculate the bending stresses in gears with asymmetric tooth profiles a standard or a simplified equation or empirical statement has not been encountered in the literature. In this study, a novel bending stress calculation procedure for gears with asymmetric tooth profiles is developed using both the DIN3990 standard and the finite element method. The bending stresses of gears with symmetrical profile were determined by the developed finite element model and was verified by comparing the results with the DIN 3990 standard. Using the verified finite element model, by changing the drive side pressure angle between 20° and 30° and the number of teeth between 18 and 100, 66 different cases were examined and the bending stresses in gears with asymmetric profile were determined. As a result of the analysis, a new asymmetric factor was derived. By adding the obtained asymmetric factor to the DIN 3390 formula, a new equation has been derived to be used in tooth bending stresses of gears with asymmetric profile. Thanks to this equation, designers will be able to calculate tooth bending stresses with high precision in gears with asymmetric tooth profile without the need for finite element analysis.

Finite Element Modeling of Selective Laser Melting 316L Stainless Steel Parts for Evaluating the Mechanical Properties

2016 ◽  
Author(s):  
Arman Ahmadi ◽  
Narges Shayesteh Moghaddam ◽  
Mohammad Elahinia ◽  
Haluk E. Karaca ◽  
Reza Mirzaeifar
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Stainless Steel ◽  
Finite Element Model ◽  
Grain Boundaries ◽  
Mechanical Response ◽  
Element Model ◽  
Polycrystalline Materials ◽  
Microstructural Properties ◽  
Laser Melting

Selective laser melting (SLM) is an additive manufacturing technique in which complex parts can be fabricated directly by melting layers of powder from a CAD model. SLM has a wide range of application in biomedicine and other engineering areas and it has a series of advantages over traditional processing techniques. A large number of variables including laser power, scanning speed, scanning line spacing, layer thickness, material based input parameters, etc. have a considerable effect on SLM process materials. The interaction between these parameters is not completely studied. Limited studies on balling effect in SLM, densifications under different processing conditions, and laser re-melting, have been conducted that involved microstructural investigation. Grain boundaries are amongst the most important microstructural properties in polycrystalline materials with a significant effect on the fracture and plastic deformation. In SLM samples, in addition to the grain boundaries, the microstructure has another set of connecting surfaces between the melt pools. In this study, a computational framework is developed to model the mechanical response of SLM processed materials by considering both the grain boundaries and melt pool boundaries in the material. To this end, a 3D finite element model is developed to investigate the effect of various microstructural properties including the grains size, melt pools size, and pool connectivity on the macroscopic mechanical response of the SLM manufactured materials. A conventional microstructural model for studying polycrystalline materials is modified to incorporate the effect of connecting melt pools beside the grain boundaries. In this model, individual melt pools are approximated as overlapped cylinders each containing several grains and grain boundaries, which are modeled to be attached together by the cohesive zone method. This method has been used in modeling adhesives, bonded interfaces, gaskets, and rock fracture. A traction-separation description of the interface is used as the constitutive response of this model. Anisotropic elasticity and crystal plasticity are used as constitutive laws for the material inside the grains. For the experimental verification, stainless steel 316L flat dog bone samples are fabricated by SLM and tested in tension. During fabrication, the power of laser is constant, and the scan speed is changed to study the effect of fabrication parameters on the mechanical properties of the parts and to compare the result with the finite element model.

Automotive Glass Exciter Technology for Acoustic Application

2014 ◽  
Author(s):  
Babak Ebrahimi ◽  
Amir Khajepour ◽  
Todd Deaville
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Experimental Studies ◽  
Element Model ◽  
Fe Model ◽  
Component Level ◽  
Modeling And Analysis ◽  
Electric Actuator ◽  
Conventional Systems ◽  
Fine Tune

This paper discusses the modeling and analysis of a novel audio subwoofer system for automotive applications using the automobile windshield glass. The use of a piezo-electric actuator coupled with a mechanical amplifier linked to a large glass panel provides a highly efficient method of producing sound. The proposed subwoofer system has the advantage over existing conventional systems of not only reducing the weight of the automobile, but also a significant power savings resulting in an increase of expected fuel economy. Among various design challenges, the glass-sealing design is of huge importance, as it affects the system dynamic response and so the output sound characteristics. The main goal in this manuscript is to evaluate different glass-sealing design configurations by providing a comprehensive Finite Element model of the system. To do so, a comprehensive, yet simplified FE model is developed, and experimental studies are performed in the component level to fine-tune and verify the model. Harmonic response of the system for each sealing configuration design is obtained in the frequency range of 0–200 Hz, and the results are compared and discussed. The finite element model is also beneficial in preliminary design of other components as well as the exciter placement, and predicting the performance of the overall system.

Mechanical response of a panel section with a hexagonally tessellated stiffener grid

2016 ◽  
Vol 231 (8) ◽  
pp. 1402-1414
Author(s):  
M Bouazizi ◽  
T Lazghab ◽  
M Soula
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Mechanical Response ◽  
Element Model ◽  
External Loading ◽  
Original Structure ◽  
Hexagonal Grid ◽  
Aircraft Fuselage ◽  
Stiffened Shells ◽  
Analytical Expressions

Stringers are stiffening members of pressurized aircraft fuselage. They provide support to the fuselage’s skin. A new stringer grid concept is proposed for conventional aircraft fuselage. Optimization is used to find the hexagonal grid that best replaces the original while keeping the same total stringer length. A finite element model is built to analyze the optimal hexagonal grid stiffened structure and compare it with the original orthogonally stiffened structure in terms of eigenfrequencies and static response to external loading. The finite element model is validated through Flugge’s analytical expressions for stiffened shells. Results show that the hexagonal grid stiffened structure yields higher eigenfrequencies with stresses and displacements comparable with that of the original structure.

scholarly journals A validated finite element study of stress shielding in a novel hybrid knee implant

2021 ◽  
Author(s):  
Ziauddin Mahboob
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Finite Element Model ◽  
Bone Tissue ◽  
Stress Shielding ◽  
Stress Transfer ◽  
Element Model ◽  
Implant Design ◽  
Polyamide 12 ◽  
Compressive Loads

This study (1) proposes a hybrid knee implant design to improve stress transfer to bone tissue in the distal femur by modifying a conventional femoral implant to include a layer of carbon fibre reinforced polyamide 12, and (2) develops a finite element model of the prosthetic knee joint, validated by comparison with a parallel experimental study. The Duracon knee system was used in the experimental study, and its geometry was modelled using CAD software. Synthetic bone replicas were used instead of cadaveric specimens in the experiments. The strains generated on the femur and implant surfaces were measured under axial compressive loads of 2000 N and 3000 N. A mesh of 105795 nodes was needed to obtain sufficient accuracy in the finite element model, which reproduced the experimental reading within 10-23% in six of the eight test locations. The model of the proposed hybrid design showed considerable improvements in stress transfer to the bone tissue at three test flexion angles of 0°, 20°, and 60°.

scholarly journals Simulation of contact interaction of piezoelectric engine elements

2019 ◽  
Vol 3 (4) ◽  
pp. 222-229
Author(s):  
A. V. Azin ◽  
S. A. Kuznetsov ◽  
S. A. Ponomarev ◽  
S. V. Ponomarev ◽  
S. V. Rikkonen
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Finite Element Model ◽  
Operation Mode ◽  
Experimental Studies ◽  
Operating Mode ◽  
Element Model ◽  
Piezo Element ◽  
Element Activity ◽  
Piezo Electric

In the article the results of a new type of piezo-electric step-engine research are presented. The original construct of piezo-electric step-engine is contained in special engineering lever called grab device that can organize back and forward rod’s motion with only one piezo element activity. To choose the effective process of piezo-electric step-engine work the mathematical model was created. This mathematical model describes inner piezo-electric step-engine process with features of contact and electroelastic deformation. Using the ANSYS application package, а finite element model of the piezo-electric step-engine has been developed. This finite element model allows estimate the stress-strain state of structural elements of the piezo-electric step-engine and determine the effective step-by-step operation mode of the piezo-electric step-engine. Using the finite element model, the influence of the piezo-electric step-engine operating mode parameters on the amount of displacement of the rod is studied. According to results of experimental studies, the proposed numerical model allows to simulate the dynamic process of step-operation of a piezo-electric step-engine with an error of no more than 6 %. This finite element model include the external load on piezo-electric step-engine and can be used to design piezo-electric step-engine of various fields of application.

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